It is known to improve the cooling conditions in the current-carrying conductors of a pole coil for electric machines and apparatus, particularly for revolving excitation windings of synchronous electric machines, by making the pole coil with an edgewise wound winding with protruding cooling fins. In such a case, the cooling fins can be formed by widening or bringing out the conductors in individual turns; the have then the same thickness as the conductor. If they they to be thinner than the conductors of the pole coil, they can be made by profiling the conductors themselves accordingly or by arranging thin metallic ribbons of larger width directly on the conductors. In this connection, reference may be had to Deutsches Gebrauchsmuster 1,842,890 and Austrian Pat. No. 105,958. One thereby obtains an increase of the heat-emitting surface of the pole coil. However, this increase of the area by cooling fins cannot go arbitrarily far, as the height of the fins must remain limited for reasons of strength and the fins cannot be set too closely together for flow reasons. SUMMARY SUMMAR OF THE INVENTION
It is an object of the invention to improve the heat transfer conditions in such a pole coil equipped with cooling fins still further.
To realize this object and according to a feature of the invention, the cooling fins in a pole coil of the kind described above are subdivided in the longitudinal direction into short sections which are bent out so that they are not aligned with each other. Through this alternating deflection of the cooling fins from their original position, the length of the cooling fins, which otherwise agrees with the length of the sides of the pole coil, is subdivided into short cooling fin sections which are offset with respect to each other. Instead of one long cooling fin, one therefore obtains several short cooling fin sections, which are disposed one behind the other and do not line up. However, this special configuration has a favorable effect on the boundary layer which forms when the cooling medium flows past and the heat transfer coefficient is increased. This means that more heat can be removed from a pole coil of the same dimensions than would be the case with cooling fins not disaligned with respect to each other. The invention affords the advantage that through special shaping in advance, or also through later deformation, the heat loss of cooling fins can be increased. This advantageous effect is found in cooling fins with transversal as well as with longitudinal flow. In each case, namely, with longitudinal flow, transversal flow or with a combination of both flow directions, an improvement of the heat transfer is achieved by the deflected, disaligned cooling fin.
The cooling fins can be subdivided into short sections which are bent out alternatingly so that they do not line up; this subdivision can be made in any desired manner, particularly periodically. Thus, one can make the cooling fins wavy, whereby short, successive, not aligned cooling fin sections are provided, even though the continuity of the cooling fin is maintained. This waviness affords the advantage that the cross-section of the current-carrying conductor, of which the cooling fin is part, is not reduced. However, the individual short sections can also be delineated by cuts, which is advisable for thicker cooling fins, and by then bending out each cooling fin section in a suitable, non-aligned manner. Each section can be bent out here toward one or both sides.
Although the invention is illustrated and described herein as a pole coil for electric machines and apparatus, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein within the scope and the range of the claims. The invention, however, together with additional objects and advantages will be best understood from the following description and in connection with the accompanying drawings.